1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor substrate such as an epitaxial substrate or the like used in formation of a semiconductor device such as a solid-state image-pickup device or the like and to a method of manufacturing a solid-state image-pickup device fabricated by using the semiconductor substrate.
2. Description of the Related Art
As a semiconductor substrate for forming a semiconductor device such as a solid-state image-pickup device or the like, a CZ substrate grown by a CZ (Czochoralski) method, an MCZ substrate grown by an MCZ (Magnetic field Czochoralski) method, an epitaxial semiconductor substrate obtained by forming an epitaxial layer on the surface of the CZ substrate or the MCZ substrate, or the like is generally used in many cases.
In particular, for a solid-state image-pickup device, an epitaxial semiconductor substrate or an MCZ substrate is mainly used so as to reduce an uneven image contrast caused by an uneven dopant concentration (Striation).
When the epitaxial semiconductor substrate of the above substrates is used, a low-resistance region can be formed under an element formation layer by forming a buried region or using a low-resistance substrate. For this reason, the epitaxial semiconductor substrate is effective for low-voltage drive or low power consumption, and the use of the epitaxial semiconductor substrate is expected to be widened in the future.
In a silicon epitaxial semiconductor substrate, a CVD (Chemical Vapor Deposition) method is used as a practical method, and the following four types of major source gases are used.
In a hydrogen reduction process, two types of source gases, i.e., SiCl4[SiCl4+2H2xe2x86x92Si+4HCl] and SiHCl3[SiHCl3+H2xe2x86x92Si+3HCl] are used.
In a thermal decomposition method, two types of source gases, i.e., SiH2Cl2[SiH2Cl2xe2x86x92Si+2HCl] and SiH4[SiH4xe2x86x92Si+2H2] are used.
Of these source gases, SiHCl3 is mainly used for a solid-state image-pickup device because SiHCL3 is expensive, and has a high growing rate to be suitable for thick-film epitaxial.
However, at present, in an epitaxial substrate formed by using any one of the source gases described above, a large amount of impurity, especially metal impurity, is mixed in the step of forming an epitaxial layer, and illuminated defects caused by a dark current of a solid-state image-pickup device cannot be sufficiently reduced in number. For this reason, the impurity is a factor that degrades characteristics or a manufacturing yield.
Therefore, the present applicant has proposed the following manufacturing method. That is, in manufacturing of an epitaxial wafer for a solid-state image-pickup device, when an element whose family is the same as that of silicon is implanted at a concentration of 1xc3x971016 cmxe2x88x923 or more in a silicon substrate before epitaxial to obtain excellent getter performance, and, by using a wafer epitaxially grown on the substrate, illuminated defects caused by a dark current of a solid-state image-pickup device can be considerably reduced in number (see Japanese Patent Application No. 6-23145).
As an example of the above method, a so-called carbon gettering in which carbon atoms are ion-implanted at a dose of 1xc3x971014 cmxe2x88x922 has been proposed in the patent application.
However, in this case, the following problem is posed. Since high-concentration carbon is implanted in a silicon surface, unevenness of the wafer surface is degraded by impact, and the wafer surface is coarsened. For this reason, bright points are degraded after epitaxial growth, and new illuminated defects caused by the bright points are degraded.
In order to solve the above problem, according to the present invention, there is provided a method of manufacturing a semiconductor substrate in which generation of bright points after epitaxial growth is reduced.
The present invention is also to provide a method of manufacturing a solid-state image-pickup device in which illuminated defects are reduced in number.
In a method of manufacturing a semiconductor substrate according to the present invention, an epitaxial layer is grown at a growth temperature of 1,120xc2x0 C. or lower to fabricate an epitaxial semiconductor substrate for a solid-state image-pickup device.
In a method of manufacturing a semiconductor substrate according to the present invention, pre-annealing is performed at a temperature of 900xc2x0 C. or lower before hydrogen annealing, and an epitaxial layer is grown after hydrogen annealing to fabricate an epitaxial semiconductor substrate for a solid-state image-pickup device.
In a method of manufacturing a semiconductor substrate according to the present invention, pre-annealing is performed at a temperature of 900xc2x0 C. or lower before hydrogen annealing, and an epitaxial layer is grown at 1,120xc2x0 C. or lower to fabricate an epitaxial semiconductor substrate for a solid-state image-pickup device.
In a method of manufacturing a solid-state image-pickup device, an epitaxial layer is grown at a growth temperature of 1,120xc2x0 C. or lower, an epitaxial layer is grown after hydrogen annealing to fabricate an epitaxial semiconductor substrate, and a solid-state image-pickup device is fabricated on the epitaxial layer of,the epitaxial semiconductor substrate.
In a method of manufacturing a solid-state image-pickup device according to the present invention, an epitaxial semiconductor substrate subjected to pre-annealing at a temperature of 900xc2x0 C. or lower before the hydrogen annealing is fabricated, and a solid-state image-pickup element is fabricated on an epitaxial layer of the epitaxial semiconductor substrate.
In a method of manufacturing a solid-state image-pickup device according to the present invention, pre-annealing is performed at a temperature of 900xc2x0 C. or lower before the hydrogen annealing, an epitaxial semiconductor substrate whose epitaxial layer is grown at a growth temperature of 1,120xc2x0 C. or lower is fabricated, and a solid-state image-pickup element is fabricated on the epitaxial layer of the epitaxial semiconductor substrate.
According to the present invention described above, pre-annealing is performed at a temperature of 900xc2x0 C. or lower, or the epitaxial layer is grown at a growth temperature of 1,120xc2x0 C. or lower, so that bright points after epitaxial growth can be reduced in number.
A solid-state image-pickup element is fabricated on the epitaxial layer of the epitaxial semiconductor substrate in which bright points are reduced in number to thereby constitute a solid-state image-pickup device, so that illuminated defects caused by the bright points can be reduced in number.